With certain malfunctions of natural valves in the body, it is desirable to replace that valve.
It is known in the art that natural heart valves can be replaced with prosthetic valves. Such replacement has heretofore generally been accomplished through major, open chest surgery. Such serious surgery results in a high mortality rate when the patient is in overt heart failure or pulmonary edema.
Recent developments have provided catheter-mounted valves which can be inserted in a major vessel at a point remote from the heart and positioned, through the vessel, proximate to a malfunctioning aortic valve thereby avoiding major surgery. One such valve, disclosed in U.S. Pat. No. 3,671,979 to Moulopoulos issued June 27, 1972, provides a conical, umbrella-like valve positioned on the end of an elongated catheter insertable so that the conical end of the valve is pointed upstream in the vessel. The distal end opens periodically, under the influence of reverse flow, to contact the inner walls of the vessel and prevent reverse flow while flow in the opposite direction collapses the valve around the catheter to allow flow in that direction. A problem presented by this type of valve is that the collapsed configuration provides areas of downstream stagnation which drastically increases the incidence of thrombus formation leading to reduction of the valving action and massive embolic complications.
Another type of catheter-mounted valve which, incidentally, is disclosed in FIGS. 3-5 of the above patent, but is not further described or claimed therein, utilizes an inflatable balloon on the end of the catheter which is periodically inflated by an external control to engage the walls of the vessel and block flow. Problems with this type of system are ineffective blockage of reverse flow and the requirement for an elaborate external control system to keep operation of the valve synchronous with the heart action.